Automatic refuse reclamation system

ABSTRACT

An automatic refuse-reclamation system wherein unprocessed municipal waste is initially separated into five distinct streams: light paper, light plastics, magnetic materials, large items and fines. The system employs many small carts that receive the large items individually, permit identification of the large items and deposite thereof in appropriate receptacles. The fines are separated from one another in a vortex classifier.

United States Patent Wilson AUTOMATIC REFUSE RECLAMATION SYSTEM June 10,1975 Smith et al 73/12 Watner 4. 198/38 lO/l972 4/1973 [75] Inventor:David G. Wilson, Cambridge, Mass. Primary Examiner koben B Reeves [73]Assignee: Massachusetts Institute of Assisi!!!" Examiner-H Gram SkaggsTechnology, Cambridge, Mass Attorney, Agent, or Firm-Arthur A. Smith,JIZ;

R I S I Filed: y 1974 ober Shaw, Martin M an a [211 App]. No.: 475,488[57] ABSTRACT An automatic refuse-reclamation system wherein un- 52 us.(:1. 209/75; 198/38; 214 11 Processed municipal waste is initiallySeparated into 51 Int. Cl. 801d 37/02 five distinct streams light P plight Plastics. g- [58] Field of Search 209/72-75, materials, largeitems and fines- The System 09 5 13; 193 3 214 11 ploys many small cartsthat receive the large items in dividually, permit identification of thelarge items and [56] References Cited deposite thereof in appropriatereceptacles. The fines UNITED STATES PATENTS are separated from oneanother in a vortex classifier.

3,747,555 7/1973 Sentenuria et al 209/1115 10 Claims, 18 Drawing FiguresIOI 1 RAW REFUSE WATER JET 6 BAG SLITTER METAL DETECTOR TRAVELLING-MESHIMPACT mn-sucnon SCREEN 'gfigg ELER METER 2A NFRA RED TRAVERSE COMPUTER2 BELT E v 17 r it 4 ELECTROMAGNET u II} 533; 1 7 2C TWO-DECK wannrmcSCREE "wk m 1 s; ART READERS 28 Q & UNLOADERS PLASTIC H M 7 18 20A 28 tL FINES r uumwmc SHEET PAPER 1-. I: OBJECT I02 2 FERROUS MATLS 9 SENSORHOPPER? 29 cam? MICELERATOR PATENTEUJUH 10 ms MAGNETIC SEPARATORMAGNETIC MATERIALS COMMINUTER TO VORTEX CLASSI Fl ER lOl SHEET 1 FEEDHOPPER LOOSE PAPER E Q AND PLASTICS 4 SEPARATOR PLASTIC PAPER FILMSHEETS II T f cARTs 3 PFINES ll'Qll 8 LARGE- f ITEMS VORTEX OUTCLASSIFIER METAL INFRARED IMPACT DETECTOR SENSOR ACCELEROMETER COMPUTERl7 CART f CODER PATENTEDJUH 10 38 I5 208 q I9A L/ l 1\ /2 IIA l3 l4 l5-4 7 7 7 METAL INFRARED IMPACT DETECTOR] SENSOR ACCELEROMETER 7 3SPECIAL-PURPOSE d COMPUTER l6 PATENTEDJUN 1 0 I975 SHEET FIG. 6A

FIG. 6B

PATENTEDJUH 10 I975 SHEET FIG.

24 FIG.

FIG. 714

ELECTRIC 4 ,9 D R/ E 7} 5 #1 -56 DRIVE critg ELECTRIC MOTOR SHEETPATENTEDJUH 10 I975 FIG. 8A

CART A cART A FIG. 86

cARTA CART 8 CART 8 PATENTEDJUH 10 I975 SHEET 1 H/sec SENSOR IOVE 7 B A+5H/sec? OBJECT SENSOR FIG. .9

CART 29 ACCELERATOR 1 AUTOMATIC REFUSE RECLAMATION SYSTEM The inventionwas made in the course ofa grant from the Environmental ProtectionAgency, Office of Solid Waste Management, an agency of the United StatesGovernment.

The present invention relates to refuse-reclamation systems that acceptunprocessed municipal waste and divide that waste into categoriesautomatically.

There accompanies herewith the Masters thesis of John Murray Malarkey,hereby incorporated by reference herein. The work upon which the thesisis based was done at MIT. under the supervision of the present inventor.The thesis contains, among other things, explanations of prior-artapproaches to refuse-relamation systems, mathematical treatment ofaspects of the present system. detailed explanation of an embodiment ofthe present system, etc., much of which is not repeated here. The thesiswas deposited in the M.I.T. library system on or about July 10, 1973.

Until recently the most serious obstacle faced by municipalities withregard to solid-waste recovery was the expense, difficulty andundesirable nature of handsorting. Two approaches exist as solutions tothis problem: (l) promoting segregation of wastes at their source (inthe home); and (2) developing less expensive and more efficient methodsof mechanical sorting. If the prime generator of municipal waste, thehouseholder, could be persuaded to separate his/her wastes at home, theproblems of sorting and decontamination would be greatly reduced becausemost contamination occurs when valuable items are mixed with undesirablematerials in common containers. However, it is realized that less thanfull cooperation can be expected from householders so that some centralmeans for sorting is necessary if efficient large-scale recycling is tobe achieved.

A number of investigations have been undertaken to determine thecomposition and quantity of solid wastes in urban areas. Samplesindicate that 40-50% of resi dential and/or municipal solid wastes arein the form of paper products, about 9% are metals, and 8% are glass.These materials, over 60% by weight, or municipal refuse all havepresent potential markets in the recycling industry.

All indications are, from a comparison of available data, that a goodproportion of the incoming refuse in the form of large relativelyhomogeneous recyclable items, e.g., tin cans, unbroken bottles, bundlesof newspapers, and paper containers, which can be salvaged for recyclingwithout further processing. This last premise forms the basis for thetheory behind the pres ent approach to handling the sorting problem. Itis felt that sufficient savings can be achieved by removing all largehomogeneous items before further size reduction to justify the cost ofthe automatic sorting equipment hereinafter discussed.

A further economic as well as practical advantage of the present systemis its flexibility. Since virtually all large items of refuse passingthrough the plant will be automatically identified, there is thecapability of choosing which particular materials have enough value inthe then existing market to justify their recovery. The plant is notconstrained to salvaging only paper, metals, and glass, though atpresent those seem to have the best potential for recycling.

Accordingly, a principal object of the present invention is to provide arefuse-reclamation system wherein size reduction of the incoming trashis minimized.

A further object is to provide a system wherein large homogeneousrecyclable items are salvaged for recycling without further processing.

These and still further objects are evident in the discussion thatfollows.

The objects of the invention are attained by a refuseseparation systemthat is operable to separate individual large items from the mass of rawrefuse introduced to the system. lt includes pre-sorter means thatincludes means for mechanically agitating the refuse to break up clumps,means to divide fines in the refuse from the large items therein, meansto remove loose paper and plastic therefrom, and preferably, means toremove magnetic particles. A plurality of carts, each being the leadingcart of a queue of carts that travel on a closedloop track, ispositioned to receive the individual large items from the pre-sortermeans. Acceleration means is provided to propel each leading cart downthe track and to accelerate the next cart in the queue into position. Anobject-detector acts to detect entry of a large item into each leadingcart and is connected to actuate the acceleration means for that cart,propulsion means being provided to move each accelerated cart around itsclosed-loop track. There is uncoupling means to disconnect thepropulsion means when a cart encounters another cart in a queue ofcarts. Sensors act to receive signature-type messages from eachindividual large item and to supply signals indicative of a plurality ofcharacteristics of the individual large item present in each cart. Thesensors are connected to means for analyzing the signals to provide anindication of the character of the individual large item sensed. Meansis included for removing the individual large items from each cart at alocation determined by the characteristics of the item as indicated bythe signals and interpreted by the means for analyzing.

The invention is hereinafter discussed with reference to theaccompanying drawing in which:

P10. 1 is a flow diagram of a system embodying the present inventiveconcepts and includes, among other things, mechanisms for separating outpaper, plastics, magnetic materials and fines to leave large items thatare received by individual carts;

FIG. 2 is a perspective view of the system, somewhat diagrammatic inform and with many details omitted;

FIG. 3 shows a portion of the system of FIGS. 1 and 2 and, inparticular, shows a front-elevation view of a diagrammaticrepresentation of a cart with the front endpiece of the cart removed toshow the interior thereof;

FIG. 4 is a diagrammatic representation of a part of said system;

FIGS. 5A, SB and 5C show a queue of the carts and an acceleratingmechanism for separating the leading cart of the queue from the othercarts, once the leading cart has received a single large item;

FIG. 6A is a plan view, partially cutaway, of a cart similar to thatshown in FIG. 3 and is intended to show a mechanism to permit removal oflarge items from the cart;

FIG. 6B is a view taken upon the line 6B-6B in FIG. 6A, looking in thedirection of the arrows;

FIGS. 7A, 7B and 7C show a mechanism on each cart to engage a pin of acog chain to drive the cart around the closed-loop track of the system;

FIGS. 8A. 8B and 8C show a latching mechanism to permit the securingtogether of a plurality of the carts at the loading region of thesystem;

FIG. 9 shows a portion of the system of FIGS. 1 and 2 with a number ofelements added thereto;

FIG. 10 is a side-elevation view. schematic in form. of a mechanism forremoving loose paper and plastic film from the raw refuse introduced tothe system; and

FIG. 11 is a side-elevation, schematic in form, view of a mechanism forremoving magnetic particles from the refuse.

A brief, overall description of the invention is now given withreference to FIGS. 1 and 2 wherein a refuse system embodying the presentconcepts is shown at 101. The system I01 includes a feed hopper l toreceive raw refuse (i.e., municipal trash) after such things as bedsprings, stoves, engine blocks and the like have been removed therefrom.The refuse is delivered to a pre sorter 5 that comprises a two-deckvibrating screen 2, a travellingmesh, air-suction screen 4 and amagnetized-belt system 3. As is hereinafter discussed in greater detail,the vibrating screen 2 acts to agitate the refuse, mechanically to breakup clumps, and it acts, as well, to divide fines in the refuse from thelarge items therein. The vibrating screen 2 is inclined from its upperor receiving end 2A downward to its lower or discharge end 28 in FIG. 2.The vibrating screen 2 consists ofa large-mesh upper screen 2C and asmall-mesh lower screen 2D. The refuse drops upon the upper screen 2Cand passes under a very-highpressure water jet (or jets) from a waterjetbag slitter 6 in FIG. 2, As the refuse items bounce along the vibratingscreen 2C, loose paper and plastic are removed therefrom by theair-suction means 4 and magnetic items by the magnet ized-belt system 3.

As the refuse moves toward the end 28, smaller items pass through thelarge-mesh screen 2C to the lower screen 2D. Fines pass through thelower screen 2D and are delivered to a vortex separator 8 (see US. Pat.No. 3,739,9l0, Wilson) in FIG. 1, through a chute 7 in FIG. 2. Largeitems are delivered to carts designated 11 in FIG. I and 11A and 118 inFIG. 2, through chutes I0 and 9, respectively, in FIG. 2. The cartsystem, which is an important part of this invention, is discussed indetail in the next few paragraphs.

By way of preliminary explanation, the cart system is designed so thatwhen the carts 11A and the carts [18 leave the chute area, each containsone large item only. The term large item" is intended to denoteindividual items such as, for example, a can, a bottle, a telephonebook, a pan, etc. A large item can be relatively homogeneous instructure (e.g., a telephone book) or it can be heterogeneous. To bevaluable, the sorted product must be relatively pure. Thus, for example,an un painted aluminum can is pure but an aluminum utensil with, say, aplastic or wood handle is not. As the carts move from the chute area, inthe direction of the arrow numbered 102, toward unloading hoppers 12,they pass a plurality of sensors that comprise at least a metal detector13, an infrared sensor 14 (see United States Pat. No. 3,747,755.Senturia et al.) and an impact accelerometer 15 (see U.S. Pat. No.3,788,466 and 3,759,085, Wilson et al.) which, in combination, act tocharacterize the large itiem in each cart. Messages from the sensors areconnected to a special-purpose computer 16 whose output is connected toa cart coder 17 which brands each cart. The carts thereafter pass cartreaders and unloaders 28 in FIG. 2, which identify the particular cartin terms of the large item in that cart and discharge the item at anappropriate hopper 12. The par ticular mechanisms to effect theforegoing functions are now discussed.

Turning first to the mostly schematic representation in FIG. 3, the cartllA thereshown is moved in a closed-loop path along tracks 20A and 20Bupon wheels 21A and ZIB by a closed-loop chain 22 leg, :1 chainveyor"sold by the Chainveyor Corporation of Florence, Kentucky). The chain ismoved in the closedloop path by an electric drive motor 23, turningthrough reduction gearing, a chainwheel gear (not shown), interactingforces being transmitted to the cart 11A through a pin 24 which contactsa drive dog 25, as later discussed in connection with FIG. 7. Lateralposition of the cart 11A is assured by guide wheels 26A and 268 thatroll along a closed-loop guide 27. The particular situation depicted inFIG. 3 is that of a cart 1 IA positioned at the unloading area where, asdetailed in later paragraphs, a hinged floor 68 of the cart is opened toeffect discharge of a large item being carried by the cart to anappropriate unloading hopper. The chain and further related elements arenot shown in FIG. 2 since that would merely complicate the alreadycluttered figure without adding anything of substance. It will beappreciated that the carts 11B are driven by a similar system. Themonitoring and unloading scheme above discussed, of course, applies toeither of the carts 1 1A or 1 B.

Returning again to FIG. 2, it will be observed that the carts 11A and11B in the region of the chutes 9 and 10 are queued. The purpose of suchqueuing and related matters are now discussed mostly with reference toFIGS. 2, SA, 58 and 5C.

As noted elsewhere herein, each of the large-item outputs of thevibrating screens 2C and 2D is eventually conveyed by belt or gravity toan appropriate closed-loop track. The specially designed passive carts11 are the essential element in this stage of the process. As anindividual object tumbles off the end of the conveyor belt into one ofthe stationary carts (of which there may be several available if severalclosed-loop tracks are used for each screen output), a detector such asthe photodetector labeled 18 in the chute 10, FIG. 2, senses itspassage, and a special circuit triggers a mechanism for rapidly removingthe cart. Proper design of the system creates a high probability of acart being loaded with only a single object.

The ability of the carts II to perform their primary function ofisolating single objects is dependent on the abilities of both thedetector 18 to discriminate individual objects sliding from the chute 9or the chute l0 and off the vibrating screen, and the cart acceleratorhereinafter discussed to punctually remove a loaded cart. With regard toaccurate detection, one is faced with the task of answering theparadoxical question what is a single object or item? For purposes ofthe present disclosure a single item is defined as any material ormaterials still held together by any means after passage over thevibrating screen 2, such that if it is lifted against gravity by anyportion or member, however large or small, the entire piece will rise.The definition admittedly is not a very strict one; intuitively itimplies that any materials that are united mechanically,electrostatically. by adhesion, or by embedding will be consideredsingle objects and. if collectively heterogeneous in nature. will beidentified as such by the sensors.

In order that a single item only be carried in a cart 11. it isnecessary that a cart be in position to receive a sin gle item and thatit be removed quickly subsequent to the deposit ofa single item therein.The queuing system noted above is discussed later with regard to FIGS.8A 8C. Acceleration of the queued carts is now discussed with referenceto FIGS. SA-SC. where the carts II are designated A, B, C and D tosimplify this explanation. The carts A-D are secured together in FIG. 5Aand move as a unit, that is, they are accelerated as a unit in thedirection of the arrow labeled 103 in FIG. 5B, and the foremost cart Ais detached from the four-cart unit in FIG. SB and moves around the pathtoward the sensors, etc. under the influence of the chain in the mannerto be described.

The acceleration of the carts is by a Scotch-yoke mechanism thatincludes a rotatable arm 30 in FIGS. SA-SC.

Since the power required in the process is nearly proportional to thenumber of carts in the queue, and to the third power of the steady-stateangular velocity of the accelerator, an attempt should be made to keepthis number as small as possible. On the other hand, it can be expectedthat the frequency of objects being fed to the carts 11 will be morethan the average value approximately 50% of the time. Surge loads of twoor more times this average frequency are quite likely. The system mustbe designed to function as well as possible with these loadfluctuations.

The accelerator comprises an electric motor 31 that drives a clutchbrake 32. The narrow horizontal arm 30 is attached to the verticaloutput shaft of the clutchbrake and is allowed to rotate through 180when the clutch is engaged. Ball bearings 30A and 30B are mounted onvertical studs set at exactly one cart-length apart on the arm 30 sothat as the first bearing just emerges from a channel provided on onevehicle the other just enters a channel provided on the trailing vehicleas shown in FIGS. SA-SC. The motion given to each cart is a part of asimple harmonic acceleration, assuming instantaneous acceleration toconstant velocity rotation of the horizontal arm. The equations ofmotion are presented in said thesis.

The photodetector discussed in said thesis has been designed so as totrigger the accelerator a small pre-set time interval after the leadingedge of a single item of refuse has broken the light path. The timedelay is determined by the distance the object must fall from the chuteto the cart below and, to a certain extent, on the average size of theobjects encountered. Difficulties arise when two or more objects areclumped together so as to appear as one or when single objects withtransverse holes" appear as more than one object. A solution to thisproblem might involve more sophisticated sensing techniques, using lightrays or otherwise. Intuitively, the greatest probability for accuratedetection would be achieved if the feed conveyor (see the conveyor shownat 40 in FIG. 9) is operated at the highest possible speed so that,while the average feed rate in objects per second is maintained, theaverage physical spacing between items would be increased and minimaloverlapping would occur.

The accelerator is a further limiting factor in the process because ofthe interrelation between speed, power, and response time. Theclutch-brake which was used approaches a maximum output rate since. asthe speed of the input increases, so also does the time required for theoutput to reach its rated speed. Diminishing returns occur withincreased motor speed and. in general, the faster and more powerfulclutch-brakes are also more sluggish, i.e.. require a longer time toreach full rated speed. A scheme to ameliorate the problems is discussedlater in connection with FIG. 9. Also, the system shown in US. Pat. No.3.673.966 (Wilson) may be used here.

The mechanism employed in latching the vehicles is shown in FIGS. 8A-8Cwith respect to the carts A and B in FIGS. 5A5C. A latch 33 is placed onthe same side of the cart as the accelerator arm 30 since it is criticalthat the vehicles be immediately adjacent here in order for theaccelerator wheels to mesh smoothly into the channels from one cart tothe next. During the normal course of travel around the track the latchis in position shown in FIG. 8A, which prevents the carts from becomingconnected while still permitting them to contact one another. Thissituation might occur if two carts are accelerated consecutively and thesecond strikes the rear of the first before the chain drive has engagedeither, or as the vehicles join the loading queue beyond the point atwhich they are required to be mechanically united.

As the carts are driven into the area where the primary queue of five tosix carts is formed, a cam 35 on the side of the track through a roller34 lifts the latch 33 of cart B to the position shown in FIG. 8B, whichallows it to unite to a stud 37 on cart A in front upon sufficientimpact force. The cam 35 has surfaces designated 35A, 35B, 35C. and 35Din this set of figures. In FIG. 8B the roller 34 rides up the surface35A to 35B as shown. As the first cart A is loaded and pushed out ofposition the cam surfaces 35C and 350 lift the head of the latch on thesucceeding vehicle to the position shown in FIG. 8C, freeing the leadcart A.

After acceleration the slower chain drive system pushes the loaded cartsaround the remainder of the circuit of FIG. 2. Further details of theinteracting mechanisms between the chain and the cart are now given withreference to FIGS. 7A-7C where the pin 24 is represented by an arrow toshow the direction of movement of the chain. Each cart has the speciallymounted drive dog 25 on its side for driving and for automatic queuing.FIG. 7A illustrates the normal position of the mechanism duringconstant-speed travel of the cart under the influence of the chaindrive. The pin 24 pushes the bottom of a link 25B of the drive dog 25and the forces are transmitted to the cart. The driving force betweenlinks 25A and 25B inhibits rotation of the link 25A in one direction anda fixed stud 25E prevents motion in the other. The force applied to thelink 25B is transmitted to the cart by the pin shown at 25C.

After dumping, as discussed elsewhere herein, the empty carts arerequired to line up behind the loading station in preparation forre-use. This stationary queue is of indeterminate length and the cartsmust be inde' pendent of the motion of the drive chain. As a driven cartapproaches the stationary queue a spring-loaded deflector on the rear ofthe last vehicle causes the link 25A to rotate through a small anglewhich is sufficient to free link 25B of its enclosure and allow it torotate through the angle (I) in FIG. 7C. As long as the vehicles areadjacent to one another the force of a spring 25D in said springloadeddeflector is sufficient to hold the mechanism in the position shown inFIG. 7C while the pin 24 from the drive chain 22 passes underneath. Whenthe cart at the loading position has been re moved, one-by-one the cartsin the queue will be advanced by the chain until all again arestationary. When a cart is accelerated from the head of the queue itwill in general be travelling initially at a speed greater than that ofthe pins 24 in the drive chain. and the link 25B will rotate to theposition shown in FIG. 78 to allow the cart to pass by one or more pins24.

Further important aspects of the carts II are now taken up withreference to FIGS. 3, 6A and 6B where the cart is again labeled 11A. Itwill be appreciated that the front-elevation view of FIG. 6B shows theinterior of the cart IIA which has inclined side walls 36 and 68. Thesingle item of refuse being carried by the cart 11A will be near theupper part 67 of a slot in the cart, being held there in the course oftransit around the loop by a filler track 38 which extends around theloop except at the region occupied by the sensors l3, l4 and 15, asshown in FIG. 4. In this way the piece of refuse is kept from falling orextending out of the cart and yet is ac cessible to the sensors.

The sensors 13, etc., obtain data from the contents of the cart andtransmit the data to the control computer 16, the data are compared withinformation previously stored in the computer and, on the basis of thiscomparison, a decision is made concerning classification of thematerial. Reference may be made to the Senturia et al. U.S. Pat. No.3,474,555 for a discussion of algorithm development for ageneral-purpose computer for this classification.

The computer-coding device employed in the system discussed in thethesis is a series of four toggle switches mounted vertically at the topand rear of each cart. A code is imprinted on the device by a bank ofsolenoids which mechanically lift the proper sequence of switches toidentify the type of material contained in the cart. (Codes for sixteendifferent categories can be presented on the four switches.) The code isconveyed on the cart to the proper dumping station where it is read by abank of micro-switches which are sensitive only to that code. A signalis subsequently relayed to an electro-mechanical actuator which opensthe vehicle floor at the appropriate time as later discussed. The latertwo functions are performed by the cart readers and unloaders 28.

The dumping operation is performed by opening the side which acts as afalse bottom or door 68. Design of the contour of the carts was chosenbecause, as noted. this configuration will be likely to cause mostobjects to lie on or near the sensor slot 67 with their long axes alongthe length of the vehicle. The floor piece is hinged at a point awayfrom the side wall labeled 69 so that its full-open position allows thegreatest free area through which objects might fall.

The bi-stable mechanism for supporting and operating the door 68 waschosen after many more complicated arrangements had provedunsatisfactory. A modest force is required to move the toggle-actiondooropening mechanism I9 through the small displacement necessary to getover top-dead center in FIG. 6B; gravity, aided by the small springforce, rapidly completes the opening action. In the system described theforce to initiate opening of the door 68 is provided by a roller 19Asecured by an arm 19B to a linkage 19. The cart readers and unloadcrscause a relay to close at an appropriate position of the track andthereby actuate a solenoid 19C which moves an appropriate cam (e.g., thecam labeled 19D in FIGS. 6A and 6B) into position to establish contactwith the roller l9A. (An air blast from above may be used to causequicker evacuation of the container.) Closing the door afte. dumping isaccomplished by the cart traveling over a second cam (not shown) mountedon the track. The cam pushes the link I9 back over top-dead center untilthe linkage I9 is again in its stable position.

The mechanism 4 for removing loose paper and plastie is shown inschematic form in FIG. [0. Loose paper and plastic lifted from thevibrating screen 2 are sucked toward a nylon open-mesh belt 53 by aircurrents caused by a fan 54. The belt 53 moves in the direction of thearrow labeled 55 by an electric-motor geared drive 56 to the region ofair jets 57 where paper is selectively removed through a funnel 58.Thereafter plasties are removed. While the belt 53 is in the vicinity ofthe funnel 58 the plastics can be retained on the belt by theelectrostatic system described in a report entitled Recovering Plasticsfrom Urban Refuse by Electrodynamic Techniques," Bureau of Mines, Dec.1972, TPR 63, and subsequently removed by other air jets 59 into anotherfunnel 60. Other systems can include the infrared sensors indicated inFIG. 2 with air blasts from the jets 57, appropriately timed.

The magnetized-belt system 3, as best shown in FIG. 11, consists of abelt 50 driven in the direction of the arrow labeled 104 by an electricmotor drive 51. Magnetic pieces that bounce upward from the vibratingscreen 2 are held by the belt 50 which is magnetized by a magnet 52 inthe region immediately above the vibrating screen 2. Such magneticparticles drop from the belt 50, as indicated by the arrow labeled 105,once the belt leaves the region of influence of the magnet 52.

Some means for automatically monitoring the various elements in FIG. 2is needed, particularly at the input end of the system 101. Onemonitoring scheme is shown in FIG. 9 which, in addition to systemelements discussed in connection with FIG. 2, includes the conveyor 40to receive single items from the vibrating screen 2. The items on thescreen 2 move in the illustrative embodiment at l foot per second,whereas the conveyor 40 moves at 5 feet per second. In this way, thesingle objects are separated from one another to assure that each cart11A will contain only one item. The object sensor 18, as shown, detectsentry of a large item into the leading cart A of the queue of carts andis connected to actuate the acceleration means, designated 29 in thisfigure, for the cart A, as before discussed. In FIG. 9, a sensor 41,which can be a multi-height, multiple-light-beam arrangement, notes thedepth of refuse on the screen 2 and is connected, as shown, back to theoutput of the feed hopper l to modulate the feed rate. A sensor 42 notesthe frequency of objects on the conveyor 40 and it also is connected tomodulate the feed rate from the feed hopper. A sensor 43 notes thelength of the queue of carts or the occurrence of a preestablishedminimum length and is connected. as shown, to control the speed of theconveyor 40 accordingly. For example, the conveyor 40 may be slowed whenthe queue reader indicates a pre-established short queue length, or thewhole system may be stopped.

Further modifications of the invention herein described will occur topersons skilled in the art and all such modifications are deemed to bewithin the spirit and scope of the invention as defined by the appendedclaims.

What is claimed is:

1. A refuse'separation system that comprises, in combination:

pre-sorter means that includes means for mechanically agitating therefuse to break up clumps and to divide fines in the refuse from thelarge items therein and means to remove loose paper and plastie;

a plurality of carts, each being the leading cart of a queue of carts ona closed-loop track, positioned to receive the individual large itemsfrom the presorter means;

acceleration means to propel each leading cart down the track and toaccelerate the next cart in queue into position;

object-detector means to detect entry of a large item into each leadingcart and connected to actuate the acceleration means for that cart;

propulsion means to move each accelerated cart around its closed-looptrack;

uncoupling means to discontinue the propulsion means when the cartencounters another cart in a queue of carts;

sensor means to provide signature-type messages from each individuallarge item and to provide a signal indicative of a plurality ofcharacteristics of the individual large item present in each cart;

means for analyzing the signal to provide an indication of the characterof the individual large item sensed; and means for removing theindividual by the characteristics of the item as indicated by saidsignal and interpreted by the means for analyzing.

2. A refuse-separation system as claimed in claim in which thepre-sorter includes magnetic means to remove magnetic materials from therefuse prior to the refuse leaving the region of the pre-sorter.

3. A refuse-separation system as claimed in claim I in which the meansfor analyzing the signal is a small speciaLpurpose computer.

4. A refuse-separating system as claimed in claim 1 in which the sensormeans includes an impact sensor and an infrared sensor.

5. A refuse-separation system as claimed in claim I in which the meansfor mechanically agitating the refuse and dividing the fines in therefuse from the large items therein comprises a multi-layer. vibratingscreen.

6. A refuse-separation system as claimed in claim 1 that furtherincludes a vortex classifier to receive the fines and to separate thesame into categories on the basis of the density of the various fines.

7. A refuse-separation system as claimed in claim 1 that includes awater-jet bag-slitter associated with the pre-sorter.

8. A refuse-separation system as claimed in claim 4 in which the sensormeans further includes a metal detector.

9. A refuse-separation system as claimed in claim I in which thepre-sorter means includes a plurality of suction means adapted to removethe newspaper and plastic.

10. A refuse-separation system as claimed in claim 1 in which the cartscontain small slits at the lower portion thereof to allow insertion ofthe sensor means therethrough to permit sensing.

1. A refuse-separation system that comprises, in combination: pre-sorter means that includes means for mechanically agitating the refuse to break up clumps and to divide fines in the refuse from the large items therein and means to remove loose paper and plastic; a plurality of carts, each being the leading cart of a queue of carts on a closed-loop track, positioned to receive the individual large items from the pre-sorter means; acceleration means to propel each leading cart down the track and to accelerate the next cart in queue into position; object-detector means to detect entry of a large item into each leading cart and connected to actuate the acceleration means for that cart; propulsion means to move each accelerated cart around its closed-loop track; uncoupling means to discontinue the propulsion means when the cart encounters another cart in a queue of carts; sensor means to provide signature-type messages from each individual large item and to provide a signal indicative of a plurality of characteristics of the individual large item present in each cart; means for analyzing the signal to provide an indication of the character of the individual large item sensed; and means for removing the individual large item from each cart at a location determined by the characteristics of the item as indicated by said signal and interpreted by the means for analyzing.
 2. A refuse-separation system as claimed in claim 1 in which the pre-sorter includes magnetic means to remove magnetic materials from the refuse prior to the refuse leaving the region of the pre-sorter.
 3. A refuse-separation system as claimed in claim 1 in which the means for analyzing the signal is a small special-purpose computer.
 4. A refuse-separating system as claimed in claim 1 in which the sensor means includes an impact sensor and an infrared sensor.
 5. A refuse-separation system as claimed in claim 1 in which the means for mechanically agitating the refuse and dividing the fines in the refuse from the large items therein comprises a multi-layer, vibrating screen.
 6. A refuse-separation system as claimed in claim 1 that further includes a vortex classifier to receive the fines and to separate the same into categories on the basis of the density of the various fines.
 7. A refuse-separation system as claimed in claim 1 that includes a water-jet bag-slitter associated with the pre-sorter.
 8. A refuse-separation system as claimed in claim 4 in which the sensor means further includes a metal detector.
 9. A refuse-separation system as claimeD in claim 1 in which the pre-sorter means includes a plurality of suction means adapted to remove the newspaper and plastic.
 10. A refuse-separation system as claimed in claim 1 in which the carts contain small slits at the lower portion thereof to allow insertion of the sensor means therethrough to permit sensing. 